Central nervous system (CNS) tumors are the second most common cancer in children. High-grade gliomas (HGGs), while representing only 8-12% of all childhood CNS tumors, are the leading cause of cancer-related death in children. Historically, pediatric HGGs are thought to be similar to adult HGGs, and current pediatric HGG therapies, which have minimal impact on improving survival, are based on preclinical and clinical studies for adult HGGs. However, recent biological, molecular, and genetic data reveal that pediatric HGGs and adult HGGs are distinct entities. Thus, the major gap in our understanding of the biology of pediatric HGGs needs to be addressed urgently. Animal models of HGGs are invaluable tools both for understanding the biology of HGGs and for preclinical testing of new therapies. The goal of this application is to develop the first mouse models of pediatric HGGs. While numerous animal models exist for adult HGGs, no animal models of pediatric HGGs are available because of two reasons: (i) previous lack of molecular and genetic information on pediatric HGGs; and (ii) technical difficulties in generating and maintaining mouse lines that closely mimic human pediatric HGGs. In this application, I will address these issues by taking advantage of recently published genetic data on pediatric HGGs and by using a combination of advanced molecular and genetic tools for manipulating gene expression in mice. These tools include Cre-LoxP mediated knockout, in utero electroporation for in vivo gene transfer, and transposon plasmids for gene expression. Two Specific Aims are proposed. In Aim 1, the most frequent and representative genetic alterations in hemispheric pediatric HGGs, including H3F3AG34R expression, PDGFRA overexpression, and Tp53 deletion, will be introduced into a subset of neural stem/progenitor cells in dorsal or ventral forebrain of mouse embryos to develop a mouse model of hemispheric HGGs. In Aim 2, the most frequent and representative genetic alterations in diffuse intrinsic pontine gliomas (DIPGs), including H3F3AK27M expression, PDGFRA overexpression, and Tp53 deletion, will be introduced into a subset of neural stem/progenitor cells in pons of the brainstem to develop a mouse model of DIPGs. This project will deliver the first mouse models of pediatric HGGs that can be used both for basic studies and for preclinical therapeutic testing. The availability of these pediatric HGG models will change the current practice of designing therapeutic strategies for pediatric HGGs based on studies of adult HGG mouse models.